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Abstract:

Systems and methods for providing vibration isolation for a MEMS device
are provided. In at least one embodiment, a system comprises a first
assembly and a second assembly, wherein the second assembly and the first
assembly are joined together, enclosing the MEMS device, wherein the
joined first assembly and the second assembly have a recessed groove
formed on an interior surface. Further, the system comprises a rigid
support encircling the MEMS device, the rigid support fitting within the
recessed groove; and at least one mount isolator in contact with a
plurality of surfaces of the rigid support, wherein the at least one
mount isolator interfaces the plurality of surfaces of the rigid support
with the first assembly and the second assembly, when the first assembly
and the second assembly are joined together.

Claims:

1. A system for providing vibration isolation for a MEMS device, the
system comprising: a first assembly; a second assembly, wherein the
second assembly and the first assembly are joined together, enclosing the
MEMS device, wherein the joined first assembly and the second assembly
have a recessed groove formed on an interior surface; a rigid support
encircling the MEMS device, the rigid support fitting within the recessed
groove; and at least one mount isolator in contact with a plurality of
surfaces of the rigid support, wherein the at least one mount isolator
interfaces the plurality of surfaces of the rigid support with the first
assembly and the second assembly, when the first assembly and the second
assembly are joined together.

2. The system of claim 1, wherein the rigid support is connected to the
MEMS device via a vibration isolator.

3. The system of claim 2, wherein the at least one mount isolator and the
vibration isolator are connected to each other.

4. The system of claim 1, wherein the plurality of surfaces of the rigid
support comprise: a distal surface, wherein the distal surface is the
surface of the rigid support that is farthest from the MEMS device, the
distal surface encircling the MEMS device; a first mount isolator surface
having a first segment of the at least one mount isolator formed thereon;
and a second mount isolator surface having a second segment of the at
least one mount isolator formed thereon, wherein the first mount isolator
surface and the second mount isolator surface are parallel to one another
and intersect opposite edges of the distal surface.

5. The system of claim 4, wherein a further segment of the at least one
mount isolator is formed on the distal surface.

6. The system of claim 4, wherein the rigid support is secured between
the first assembly and the second assembly through pressure applied by
the first assembly on the first segment of the at least one mount
isolator and pressure applied by the second assembly on the second
segment of the at least one mount isolator.

7. The system of claim 6, wherein the pressure applied to the first
segment of the at least one mount isolator and the second segment of the
at least one mount isolator causes a portion of the first segment and the
second segment to flow over a portion of the distal surface.

8. The system of claim 4, wherein an exposed portion of the rigid support
that faces the first assembly and the second assembly are not in contact
with the at least one mount isolator.

9. The system of claim 8, wherein the exposed portion comprises a
plurality of exposed strips that are periodically located around the
circumference of the rigid support, wherein an exposed strip extends
around the first surface, the second surface, and the distal surface.

10. The system of claim 9, wherein a central isolator band extends around
the circumference of the rigid support, where the central isolator band
is in contact with a portion of the distal surface that is centrally
located between the edges of the distal surface.

11. The system of claim 1, wherein the recessed groove is formed on an
interior surface of the second assembly.

12. The system of claim 1, wherein the at least one mount isolator
comprises at least one key portion, wherein the at least one key portion
is larger than surrounding portions of the at least one mount isolator,
wherein the recessed groove comprises at least one keyed section that
receives the at least one key portion of the at least one mount isolator.

13. An apparatus for attenuating vibrations for a MEMS device, the
apparatus comprising: a vibration isolator connected to and encircling
the MEMS device; a rigid support coupled to the vibration isolator, the
rigid support encircling the vibration isolator, wherein the rigid
support comprises: a distal surface, wherein the distal surface is the
surface of the rigid support that is farthest from the MEMS device, the
distal surface encircling the MEMS device; a first mount isolator surface
having a first segment of at least one mount isolator formed thereon,
wherein the at least one mount isolator and the vibration isolator
attenuate shocks and vibrations in different frequency ranges; and a
second mount isolator surface having a second segment of the at least one
mount isolator formed thereon, wherein the first surface and the second
surface are parallel to one another and intersect opposite edges of the
distal surface.

14. The apparatus of claim 13, wherein the at least one isolator covers a
portion of the distal surface.

15. The apparatus of claim 13, wherein the at least one mount isolator is
formed from an elastomeric material.

16. The apparatus of claim 13, wherein an exposed portion of the first
surface, the second surface, and the distal surface are not in contact
with the at least one isolator.

17. The apparatus of claim 13, wherein the vibration isolator connects to
the MEMS device via an inner member that encircles the MEMS device.

18. A method for attenuating vibration for a MEMS device, the method
comprising: locating the MEMS device within a rigid support, wherein a
plurality of surfaces of the rigid support are in contact with at least
one mount isolator; placing the MEMS device and the rigid support within
a groove formed in a second assembly; joining the second assembly to a
first assembly, wherein both the first assembly and the second assembly
apply pressure to the at least one mount isolator such that the location
of the rigid support is secured with respect to the joined first assembly
and second assembly.

19. The method of claim 18, further comprising adjusting at least one of
the hardness, thickness, and contact area of the at least one mount
isolator to attenuate frequencies within a certain frequency range.

20. The method of claim 19, wherein the at least one mount isolator
attenuates frequencies greater than 2000 Hz.

Description:

BACKGROUND

[0001] Vibration and shock inputs to electronic, mechanical, and
electromechanical systems can degrade the performance and operational
life of the systems. Micro Electrical Mechanical System (MEMS) devices
exemplify one such system that is particularly sensitive to vibration and
shock inputs. Frequently, to protect MEMS devices in harsh vibration
environments, vibration isolators are commonly used to attenuate the
effects of the vibrations. However, these vibration isolators are
suboptimal for attenuating shock inputs that routinely accompany the
vibrations in typical MEMS applications. For example, a MEMS inertial
measurement unit that employs MEMS sensors often has critically sensitive
frequencies that are higher than the frequencies attenuated by typical
vibration isolators. When the MEMS device is subjected to these shocks at
the high critically sensitive frequencies, the performance of the MEMS
device degrades.

[0002] Further, MEMS devices are mounted within housing assemblies. As
some MEMS devices are designed to provide precise measurements, the
mounting within the housing assemblies are designed to precise tolerances
to increase the accuracy of the measurements. Due to these precise
tolerances, the housing assemblies and MEMS devices can be difficult to
design and manufacture.

SUMMARY

[0003] Systems and methods for providing vibration isolation for a MEMS
device are provided. In at least one embodiment, a system comprises a
first assembly and a second assembly, wherein the second assembly and the
first assembly are joined together, enclosing the MEMS device, wherein
the joined first assembly and the second assembly have a recessed groove
formed on an interior surface. Further, the system comprises a rigid
support encircling the MEMS device, the rigid support fitting within the
recessed groove; and at least one mount isolator in contact with a
plurality of surfaces of the rigid support, wherein the at least one
mount isolator interfaces the plurality of surfaces of the rigid support
with the first assembly and the second assembly, when the first assembly
and the second assembly are joined together.

DRAWINGS

[0004] Understanding that the drawings depict only exemplary embodiments
and are not therefore to be considered limiting in scope, the exemplary
embodiments will be described with additional specificity and detail
through the use of the accompanying drawings, in which:

[0005]FIG. 1 is an exploded view of a housed MEMS device in one
embodiment described in the present disclosure;

[0006]FIG. 2 is an exploded view of vibration isolated inertial sensors
in one embodiment described in the present disclosure;

[0007]FIG. 3 is a cross sectional view of the interface between a MEMS
device and a housing assembly in one embodiment described in the present
disclosure;

[0008] FIGS. 4A and 4B are diagrams illustrating the mounting of a MEMS
device within a housing assembly in one embodiment described in the
present disclosure;

[0009] FIGS. 5A and 5B are diagrams of a mount isolator in multiple
embodiments described in the present disclosure;

[0010]FIG. 6 is a graph illustrating the frequency response to shocks and
vibrations of a MEMS device mounted within a housing assembly in one
embodiment described in the present disclosure; and

[0011]FIG. 7 is a flow diagram of a method for mounting a MEMS device
within a housing assembly in one embodiment described in the present
disclosure.

[0012] In accordance with common practice, the various described features
are not drawn to scale but are drawn to emphasize specific features
relevant to the exemplary embodiments.

DETAILED DESCRIPTION

[0013] In the following detailed description, reference is made to the
accompanying drawings that form a part hereof, and in which is shown by
way of illustration specific illustrative embodiments. However, it is to
be understood that other embodiments may be utilized and that logical,
mechanical, and electrical changes may be made. Furthermore, the method
presented in the drawing figures and the specification is not to be
construed as limiting the order in which the individual steps may be
performed. The following detailed description is, therefore, not to be
taken in a limiting sense.

[0014] A high frequency mount isolator can be molded, coated, or assembled
between a rigid support of a MEMS device and the housing assembly
enclosing the MEMS device. The mount isolator can be tuned to improve
attenuation of high frequency shocks and vibrations that affect the
performance of the MEMS device. In certain embodiments, the mount
isolator can function with a vibration isolator assembled between the
rigid support of the MEMS device and the MEMS device itself. The
combination of the mount isolator and the vibration isolator provide a
dual stage isolation system where the combination of the vibration
isolator and the mount isolator is tuned to attenuate shocks and
vibrations in both a lower frequency region and a higher frequency
region.

[0015]FIG. 1 is an exploded view of a housed MEMS device 100, where a
housing assembly 120 encloses an isolated MEMS device 108. In certain
embodiments, the isolated MEMS device 108 functions as an inertial sensor
assembly (ISA) and includes devices such as accelerometers and
gyroscopes. For example, the MEMS device 108 includes three
accelerometers that aid in measuring acceleration along three orthogonal
axes and three gyroscopes that provide measurements of rotation about
three orthogonal axes. When the MEMS device 108 functions as an ISA, the
inertial sensors provide inertial data, such as linear acceleration and
angular rate information, to a navigation computer onboard an aircraft or
other moving vehicle. The navigation computer processes the data for
flight control and/or navigation of the aircraft. While MEMS device 108
can provide inertial data to a navigational computer when the MEMS device
108 is an ISA, vehicle maneuvers (such as acceleration, changes in pitch,
roll and yaw, takeoff and landing), turbulence, and engine operation
generate shocks and vibrations that are conveyed through the vehicle to a
housing assembly 120 enclosing the ISA. The shocks and vibrations may
cause linear or angular acceleration errors and angular rate errors in
inertial data provided by the ISA to the navigational computer.

[0016] In certain embodiments, to prevent the shocks and vibrations from
causing linear or angular acceleration or angular rate errors in the data
provided by the MEMS device 108, the MEMS device 108 is mounted within
the housing assembly 120 through at least one mount isolator 118 and a
frequency vibration isolator 116 that attenuates the effects of shocks
and vibrations on the MEMS device 108. The mount isolator 118 is designed
to prevent rigid structures of the housing assembly 120 from contacting a
rigid support 117 that supports the MEMS device 108 within the housing
assembly. Further, in certain embodiments, the mount isolator 118
attenuates the effects of high frequency shocks and vibrations on the
MEMS device 108 and the vibration isolator 116 attenuates the effects of
low frequency shocks and vibrations on the MEMS device 108. In contrast,
the mount isolator 118 can attenuate the effects of low frequency shocks
and vibrations on the MEMS device 108 and the vibration isolator 116
attenuates the effects of high frequency shocks and vibrations on the
MEMS device 108. In alternative embodiments, MEMS device 108 connects
directly to a rigid support 117 coated by the mount isolator 118 without
an interceding vibration isolator 116. In at least one embodiment, a
retainer ring 110 secures the components of the MEMS device 108 to the
vibration isolator 116 and the mount isolator 118.

[0017] The housing assembly 120 containing the MEMS device 108 includes
both a first assembly 104 and a second assembly 112. Both the first
assembly 104 and the second assembly 112 connect to each other to enclose
and protect the MEMS device 108 while providing a mounting interface 122a
and 122b to a larger navigational system. For example, a mounting
interface 122a and 122b may include a flange through which the housing
assembly 120 is bolted to another system. In at least one embodiment, the
first assembly 104 and the second assembly 112 are placed against each
other and then secured to one another through a series of bolts 102. In
at least one implementation, an O-ring may be placed between the first
assembly 104 and the second assembly 112 such that when the bolts 102
secure the first assembly 104 against the second assembly 112, the O-ring
is pressed and flows to form a seal that protects devices within the
housing assembly 120.

[0018] In certain embodiments, the second assembly 112 has a groove 109
formed therein to receive the mount isolator 118 that encircles the MEMS
device 108. In an alternative embodiment, the groove 109 is formed in a
combination of the first assembly 104 and the second assembly 112.
Further, the groove is formed only in the first assembly 104. The mount
isolator 118 is secured in the groove between the first assembly 104 and
the second assembly 112 when the first assembly 104 and the second
assembly 112 are joined together. In at least one implementation, the
groove 109 includes a keyed section 124 that receives a key portion 123
of the mount isolator 118. The key portion 123 fits into the keyed
section 124 when the mount isolator 118 is placed within the groove 109
to prevent rotation of the MEMS device 108 within the housing assembly
120.

[0019] In at least one implementation, to secure the mount isolator 118
between the first assembly 104 and the second assembly 112, both the
first assembly 104 and the second assembly 112 apply pressure to the
mount isolator 118 such that when bolts 102 tighten the first assembly
104 against the second assembly 112, the rigid support 117 and mount
isolator 118 become securely disposed within the housing assembly 120. By
securing the rigid support 117 and mount isolator 118 between the first
assembly 104 and the second assembly 112, the MEMS device 108 is secured
within the connected first assembly 104 and the second assembly 112. The
pressure applied to the mount isolator 118 due to the fastening of the
first assembly 104 to the second assembly 112 is described in greater
detail below with regards to FIG. 3

[0020] In a further embodiment, the MEMS device 108 electrically
communicates with an external system or device by providing electronic
signals through an electrical connection 106 that electrically connects
the MEMS device 108 to an external interface 114 for transmitting and
receiving electrical signals from the external system or device such as a
navigational computer. In at least one embodiment, the electrical
connection 106 includes flex tape, a series of wires, and the like. Due
to the electrical connection 106, the MEMS device 108 is able to
communicate with an external system while being isolated within the
housing assembly 120. Thus, the MEMS device 108 is isolated within the
conjoined first assembly 104 and second assembly 112, which first
assembly 104 and second assembly 112 apply pressure to the rigid support
117 via the mount isolator 118. Further, as the rigid support 117 is
connected to the MEMS device 108 via the vibration isolator 116, the MEMS
device 108 is securely disposed within the housing assembly 120. Due to
the vibration and shock isolation and the secure location within the
housing assembly 120, the MEMS device 108 is less susceptible to both
high and low frequency shocks and vibrations.

[0021]FIG. 2 is an exploded view of one embodiment of an isolated MEMS
device 200. For example, the vibration isolator 116 may be a ring shaped
elastomeric member that encircles an ISA mount 212. In certain
embodiments, the vibration isolator 116 functions together with the mount
isolator 118 on the rigid support 117 to provide a dual stage shock and
vibration isolator that protects components joined to the ISA mount 212
from both high and low frequency shocks and vibrations. The ISA mount
212, as described herein, may connect to both an accelerometer assembly
204 and a gyroscope assembly 208. A series of accelerometer mounting
bolts 202 may secure the accelerometer assembly 204 to the ISA mount 212.
Likewise, a series of gyroscope bolts 210 may secure the gyroscope
assembly 208 to the ISA mount 212.

[0022] In at least one embodiment, the accelerometer assembly 204 includes
at least three accelerometers that are capable of measuring acceleration
along three different axes. Similarly, the gyroscope assembly 208
includes at least three gyroscopes that are capable of measuring rotation
about three different axes. Further, the ISA mount 212 provides an
external connection 214 to both the accelerometer assembly 204 and the
gyroscope assembly 208, where the external connection 214 provides an
electrical transmission path between both the accelerometer assembly 204
and the gyroscope assembly 208, where the external connection 214 enables
an external system to electrically connect through the first assembly 104
in FIG. 1 and the electrical connection 106 to receive signals from both
the accelerometer assembly 204 and the gyroscope assembly 208.

[0023] In certain embodiments, where both the accelerometer assembly 204
and the gyroscope assembly 208 are joined to the ISA mount 212, the
combination of the vibration isolator 116 and the mount isolator 118
protect both the accelerometer assembly 204 and the gyroscope assembly
208 from shocks and vibrations that affect the first assembly 104 and the
second assembly 112 in FIG. 1. Further, the combination of the vibration
isolator 116 and the mount isolator 118 protect both the accelerometer
assembly 204 and the gyroscope assembly 208 from low and high frequency
shocks and vibrations. In an alternative embodiment, only a mount
isolator 118 protects the accelerometer assembly 204 and the gyroscope
assembly 208 from shocks and vibrations that affect the first assembly
104 and the second assembly 112 in FIG. 1. When only the mount isolator
118 protects against shocks and vibrations, the ISA mount 212 directly
connects to the rigid support 117.

[0024]FIG. 3 is a cross sectional view 300 of the ISA mount 212 described
in FIG. 2 that illustrates how the ISA mount 212 is secured between the
conjoined first assembly 104 and second assembly 112 described in FIG. 1.
In certain embodiments, ISA mount 212 interfaces with both the first
assembly 104 and the second assembly 112 through the combination of the
vibration isolator 116, the rigid support 117 and the mount isolator 118.
For example, rigid support 117 connects to ISA mount 212, such that when
rigid support 117 is secured within the conjoined first assembly 104 and
second assembly 112, the ISA mount 212 is secured with respect to the
first assembly 104 and the second assembly 112. In certain embodiments,
the rigid support 117 is connected to a mount isolator 118. The mount
isolator 118 functions to prevent rigid surfaces of the rigid support 117
from contacting rigid surfaces of the first assembly 104 and the second
assembly 112. By preventing the surfaces of the rigid support 117 from
contacting rigid surfaces of the first assembly 104 and the second
assembly 112, the mount isolator 118 attenuates high frequency shocks and
vibrations that affect the first assembly 104 and the second assembly
112. In at least one embodiment, the mount isolator 118 is fabricated
from an elastomeric material or other material that is capable of
attenuating high frequency shocks and vibrations. In at least one
implementation, the mount isolator 118 and the vibration isolator 116 are
fabricated from the same elastomeric material.

[0025] In certain embodiments, the rigid support 117 connects to the ISA
mount 212 through a vibration isolator 116 that encircles the ISA mount
212. In at least one implementation, the vibration isolator 116
attenuates shocks and vibrations in a lower frequency region than the
shocks and vibrations attenuated by the mount isolator 118. The vibration
isolator 116 is described in detail in U.S. Pat. No. 5,890,569 entitled
"VIBRATION ISOLATION SYSTEM FOR AN INERTIAL SENSOR ASSEMBLY" filed on
Jun. 6, 1997, herein incorporated in its entirety by reference and
referred to herein as the '569 patent.

[0026] In certain embodiments, the vibration isolator 116 interfaces with
the ISA mount 212 through an inner member 318, where the inner member
encircles the ISA mount 212 and is encircled by and is concentric with
the vibration isolator 116. In certain implementations, the inner member
318 includes radially extending ridges that extend into the vibration
isolator 116, where the ridges increase the surface area of the inner
member 318 that is available to affix to the vibration isolator 116. In a
further implementation, the vibration isolator 116 can include cutout
regions that are concentric with the rigid support 117 and the inner
member 318, the cutout regions are further described in the '569 patent.
The shape of the cutout regions provide flexibility to the vibration
isolator 116, where the flexibility aids in damping and absorbing
unwanted shock and vibration energy transmitted through the rigid support
117.

[0027] In at least one embodiment, the rigid support 117 and the inner
members 318 are manufactured of an aluminum alloy or other rigid
material. In certain embodiments, both the vibration isolator 116 and the
mount isolator 118 are formed by the injection molding. For example, a
silicone rubber elastomeric material is injection molded under high
temperature and pressure into a cavity between the rigid support 117 and
the inner members 318 and around the rigid support 117. The silicone
rubber material bonds to the surfaces of the rigid support 117 and the
inner member 318, which silicone rubber material holds the rigid support
117 to the inner member 318. In at least one implementation, the
vibration isolator 116 and the mount isolator 118 are contiguously formed
around the rigid support 117 as shown in FIG. 3. In an alternative
embodiment, the mount isolator 118 is not contiguously formed with the
vibration isolator 116 as shown in FIGS. 4A and 4B.

[0028] In certain embodiments, to secure the rigid support 117 and the
mount isolator 118 with respect to the first assembly 104 and the second
assembly 112. The rigid support 117 and mount isolator 118 are inserted
within a groove 109 formed within the second assembly 112. The second
assembly 112 includes a second assembly surface 316 that contacts a
second mount isolator surface 314. Also, the first assembly 104 includes
a first assembly surface 312 that contacts a first mount isolator surface
310. As shown in FIG. 3, the second assembly surface 316 is the surface
of the groove 308 formed within the second assembly 112 that is farthest
from the first assembly 104. Also, the first assembly surface 312 is the
surface of the first assembly 104 that is substantially parallel to and
also nearest to the second assembly surface 316 when the first assembly
104 and the second assembly are joined to one another. The first mount
isolator surface 310 and the second mount isolator surface 314
respectively face the first assembly surface 312 and the second assembly
surface 316. Further, the first mount isolator surface 310 and the second
mount isolator surface 314 are located on opposite faces of the rigid
support 117. In certain embodiments, the combination of the mount
isolator 118 and rigid support 117 are secured with respect to the joined
first assembly 104 and the second assembly 112 by force applied against
the first mount isolator surface 310 by the first assembly surface 312
and by force applied against the second mount isolator surface 314 by the
second assembly surface 316. Because the first assembly surface 312 and
the second assembly surface 316 face each other, the force applied by the
first assembly 104 against the mount isolator 118 and the force applied
by the second assembly 112 against the mount isolator 118 are in opposite
directions. The opposing forces fix the mount isolator 118 and rigid
support 117 within the groove 308 formed in the second assembly 112.

[0029] FIGS. 4A and 4B illustrate the securing of the position of an ISA
mount 212 with respect to a first assembly 104 and second assembly 112.
The ISA mount 212 is joined to the vibration isolator 402, which is in
turn joined to the rigid support 406. In contrast to the example
described in relation to FIG. 3, where the vibration isolator 116 and the
mount isolator 118 were contiguously formed around the rigid support 117,
in certain embodiments, as shown in FIGS. 4A and 4B, a mount isolator 404
is only in contact with the surfaces of the rigid support 406 that are
orthogonally oriented to the surface of the rigid support 406 that is in
contact with the vibration isolator 402. In FIG. 4A, the ISA mount 212,
the vibration isolator 402, the rigid support 406, and the mount isolator
404, are inserted into a groove 109 formed in the second assembly 112.
When the ISA mount 212 and vibration isolators are inserted into the
groove 109, the second mount isolator surface 414 is placed against the
second assembly surface 416, where the second mount isolator surface 414
and the second assembly surface 416 function as second mount isolator
surface 314 and second assembly surface 316 described in relation to FIG.
3. In at least one embodiment, due to the elastomeric quality of the
mount isolator 404, the groove 109 and rigid support 406 can be designed
according to relaxed tolerances as the compression of the mount isolator
404 causes the mount isolator 404 to flow between the rigid support 406
and the surfaces of the first assembly 104 and the second assembly 112 in
the groove 109.

[0030] As illustrated in FIG. 4A, when the ISA mount 212 and the vibration
isolators are inserted into the groove 109, the second assembly 112 is
not in contact with the first assembly 104. In certain embodiments, as
illustrated in FIG. 4B, the first assembly 104 is joined to the second
assembly 112 such that a first assembly surface 412 comes into contact
with the first mount isolator surface 410, where the first assembly
surface 412 and the first mount isolator surface 410 function as the
first assembly surface 312 and the first mount isolator surface 310 in
FIG. 3. When the first assembly 104 is brought into contact with the
second assembly 112, the mount isolator 404 is compressed such that the
mount isolator 404 flows around the edges of the first assembly surface
412 and the second assembly surface 416. Further, when there is no mount
isolator formed on the distal surface of the rigid support 406 that is
farthest from the ISA mount 212, a portion of the mount isolator 404
flows around the distal surface of the rigid support 406 to prevent the
surfaces of the second assembly 112 from contacting the rigid support
406. As the mount isolator 404 is compressed between the first assembly
104, the second assembly 112, and the rigid support 406, the compressive
force on the mount isolator 404 holds the ISA mount 212 securely within
the space enclosed by the joined first assembly 104 and the second
assembly 112.

[0031] FIGS. 5A and 5B illustrate different embodiments of mount isolators
504. As described above, the combination of the mount isolators 504 and
the vibration isolator 502 provide a dual stage frequency response. For
example, the vibration isolator 502 attenuates the effects of shocks and
vibration that are in a lower frequency range, while the mount isolator
504 attenuates the effects of shocks and vibration that are in a higher
frequency range. Further, the frequency response of the mount isolator
504 can be controlled by altering the characteristics of the mount
isolator 504 and the compressive force that is applied to the mount
isolator 504 by the first assembly 104 and the second assembly 112. For
example, characteristics of the mount isolator 504 that can be altered to
control the frequency response of the mount isolator 504 include the
thickness, shape, and rigidity of the mount isolator 504. As the
characteristics are changed, the frequency response is determined by how
rigidly secure the mount isolator 504 is within the housing assembly 120.
For example, as the thickness increases of the mount isolator 504, the
first assembly 104 and the second assembly 112 can compress the mount
isolator 504 with greater pressure. The increase in pressure causes the
mount isolator 504 to respond to higher frequencies. Likewise, an
increase in the rigidity also causes the mount isolator 504 to respond to
higher frequencies. Generally, as the characteristics of the mount
isolator 504 change to stiffen the mount isolator 504, the mount isolator
504 will respond to higher frequencies.

[0032] As illustrated in FIG. 5A, the mount isolator 504a exposes portions
520 of the rigid support 506 at intervals as the mount isolator 504a
extends around the rigid support 506. In certain embodiments, the mount
isolator 504a is removed at the exposed portions 520 of the rigid support
506. Alternatively, the mount isolator 504a is thinner at the exposed
portions 520 of the rigid support 506 than at the non-exposed portions of
the rigid support 506. Further, the frequency response of the mount
isolator 504a is a square function of the area covered by the exposed
portions.

[0033]FIG. 5B illustrates a mount isolator 504b that includes a central
isolator band 524 that extends around the rigid support 506 and through
the exposed portions 520 of the rigid support 506. The central isolator
band 524 can further change the frequency response of the mount isolator
504b. Further, the central isolator band 524 prevents the exposed
portions of the rigid support 506 from coming into contact with metal
surfaces on the first and second assemblies 104 and 112 that contain the
mount isolator 504b. In certain embodiments, when metal surfaces on the
first and second assemblies come into contact with the rigid support 506,
the ability of the mount isolator 504b to attenuate shocks and vibrations
becomes decreased. Further, in certain embodiments, the central isolator
band 524 is separated from metal surfaces on the first and second
assemblies 104 and 112 by an air gap, where the air gap is maintained by
pressed portions of the mount isolator 504b that are located on surfaces
that are orthogonal to the surface in contact with the central isolator
band 524.

[0034] As illustrated in both FIGS. 5A and 5B, a mount isolator 504 can
include a key portion 522. As used herein, the phrase "key portion"
refers to a portion of the mount isolator that is larger than surrounding
portions of the mount isolator. In certain embodiments, a groove formed
in either or both of a first assembly and second assembly (such as first
assembly 104 and second assembly 112) may have a keyed section that is
recessed according to the shape of the key portion 522. When the rigid
support 506 and mount isolator 504 are inserted into the groove, the key
portion 522 is located within the keyed section of the groove such that
an ISA mount is placed at the same angular location within a housing
assembly when the first assembly and the second assembly are joined
together, where the housing assembly, first assembly, and second assembly
function as the housing assembly 120, first assembly 104, and second
assembly 112 in FIG. 1. Further the key portion 522 inhibits the rotation
of the ISA mount within the housing assembly.

[0035]FIG. 6 is a graph 600 of the frequency response of the combination
of a vibration isolator and a mount isolator. As illustrated, the graph
600 has two peaks, a first peak 602 and a second peak 604. The first peak
602 corresponds to the frequency response of a vibration isolator. The
second peak 604 corresponds to the frequency response of a mount
isolator. As illustrated in graph 600, the first peak 602 amplifies
signals around 250 Hz and attenuates signals above 250 Hz, the signals
are amplified at 250 Hz because 250 Hz is the natural frequency of the
vibration isolator. However, as the frequency of the shocks and
vibrations increases, the ability to attenuate shocks and vibrations of
the vibration isolator, illustrated as first peak 602, decreases. The
mount isolator amplifies signals around 4 kHz but attenuates signals
above 4 kHz such that high frequency shocks and vibrations are inhibited
from affecting the operation of MEMS devices that are isolated by the
mount isolator and the vibration isolator. In an alternative embodiment
the first peak 602 corresponds to the frequency response of the mount
isolator and the second peak 604 corresponds to the frequency response of
the vibration isolator.

[0036]FIG. 7 is a flow diagram of a method 700 for securing a mount
isolator within a housing assembly. Method 700 proceeds at 702 where a
MEMS device is located within a rigid support. For example, the MEMS
device is located within a rigid support having multiple surfaces that
are in contact with a mount isolator. In certain embodiments, the mount
isolator includes an elastomeric layer formed on surfaces of the rigid
support. Method 700 proceeds at 704 where the MEMS device and the rigid
support are placed within a groove formed in a second assembly. For
example, the rigid support extends circumferentially around the MEMS
device and slides into a groove formed in the interior surface of the
second assembly.

[0037] Method 700 proceeds at 706, where the second assembly is joined to
a first assembly. For example, the first assembly and the second assembly
are two parts of a housing assembly that encloses the MEMS device and the
rigid support. When the second assembly and the first assembly are joined
together, both the first assembly and the second assembly apply pressure
to the mount isolator formed on the rigid support such that the rigid
support and the MEMS device are secured with respect to the joined first
assembly and second assembly.

Example Embodiments

[0038] Example 1 includes a system for providing vibration isolation for a
MEMS device, the system comprising: a first assembly; a second assembly,
wherein the second assembly and the first assembly are joined together,
enclosing the MEMS device, wherein the joined first assembly and the
second assembly have a recessed groove formed on an interior surface; a
rigid support encircling the MEMS device, the rigid support fitting
within the recessed groove; and at least one mount isolator in contact
with a plurality of surfaces of the rigid support, wherein the at least
one mount isolator interfaces the plurality of surfaces of the rigid
support with the first assembly and the second assembly, when the first
assembly and the second assembly are joined together.

[0039] Example 2 includes the system of Example 1, wherein the rigid
support is connected to the MEMS device via a vibration isolator.

[0040] Example 3 includes the system of Example 2, wherein the at least
one mount isolator and the vibration isolator are connected to each
other.

[0041] Example 4 includes the system of any of Examples 1-3, wherein the
plurality of surfaces of the rigid support comprise: a distal surface,
wherein the distal surface is the surface of the rigid support that is
farthest from the MEMS device, the distal surface encircling the MEMS
device; a first mount isolator surface having a first segment of the at
least one mount isolator formed thereon; and a second mount isolator
surface having a second segment of the at least one mount isolator formed
thereon, wherein the first mount isolator surface and the second mount
isolator surface are parallel to one another and intersect opposite edges
of the distal surface.

[0042] Example 5 includes the system of Example 4, wherein a further
segment of the at least one mount isolator is formed on the distal
surface.

[0043] Example 6 includes the system of any of Examples 4-5, wherein the
rigid support is secured between the first assembly and the second
assembly through pressure applied by the first assembly on the first
segment of the at least one mount isolator and pressure applied by the
second assembly on the second segment of the at least one mount isolator.

[0044] Example 7 includes the system of Example 6, wherein the pressure
applied to the first segment of the at least one mount isolator and the
second segment of the at least one mount isolator causes a portion of the
first segment and the second segment to flow over a portion of the distal
surface.

[0045] Example 8 includes the system of any of Examples 4-7, wherein an
exposed portion of the rigid support that faces the first assembly and
the second assembly are not in contact with the at least one mount
isolator.

[0046] Example 9 includes the system of Example 8, wherein the exposed
portion comprises a plurality of exposed strips that are periodically
located around the circumference of the rigid support, wherein an exposed
strip extends around the first surface, the second surface, and the
distal surface.

[0047] Example 10 includes the system of Example 9, wherein a central
isolator band extends around the circumference of the rigid support,
where the central isolator band is in contact with a portion of the
distal surface that is centrally located between the edges of the distal
surface.

[0048] Example 11 includes the system of any of Examples 1-10, wherein the
recessed groove is formed on an interior surface of the second assembly.

[0049] Example 12 includes the system of any of Examples 1-11, wherein the
at least one mount isolator comprises at least one key portion, wherein
the at least one key portion is larger than surrounding portions of the
at least one mount isolator, wherein the recessed groove comprises at
least one keyed section that receives the at least one key portion of the
at least one mount isolator.

[0050] Example 13 includes an apparatus for attenuating vibrations for a
MEMS device, the apparatus comprising: a vibration isolator connected to
and encircling the MEMS device; a rigid support coupled to the vibration
isolator, the rigid support encircling the vibration isolator, wherein
the rigid support comprises: a distal surface, wherein the distal surface
is the surface of the rigid support that is farthest from the MEMS
device, the distal surface encircling the MEMS device; a first mount
isolator surface having a first segment of at least one mount isolator
formed thereon, wherein the at least one mount isolator and the vibration
isolator attenuate shocks and vibrations in different frequency ranges;
and a second mount isolator surface having a second segment of the at
least one mount isolator formed thereon, wherein the first surface and
the second surface are parallel to one another and intersect opposite
edges of the distal surface.

[0051] Example 14 includes the apparatus of Example 13, wherein the at
least one isolator covers a portion of the distal surface.

[0052] Example 15 includes the apparatus of any of Examples 13-14, wherein
the at least one mount isolator is formed from an elastomeric material.

[0053] Example 16 includes the apparatus of any of Examples 13-15, wherein
an exposed portion of the first surface, the second surface, and the
distal surface are not in contact with the at least one isolator.

[0054] Example 17 includes the apparatus of any of Examples 13-16, wherein
the vibration isolator connects to the MEMS device via an inner member
that encircles the MEMS device.

[0055] Example 18 includes a method for attenuating vibration for a MEMS
device, the method comprising: locating the MEMS device within a rigid
support, wherein a plurality of surfaces of the rigid support are in
contact with at least one mount isolator; placing the MEMS device and the
rigid support within a groove formed in a second assembly; joining the
second assembly to a first assembly, wherein both the first assembly and
the second assembly apply pressure to the at least one mount isolator
such that the location of the rigid support is secured with respect to
the joined first assembly and second assembly.

[0056] Example 19 includes the method of Example 18, further comprising
adjusting at least one of the hardness, thickness, and coverage area of
the at least one mount isolator to attenuate frequencies within a certain
frequency range.

[0057] Example 20 includes the method of Example 19, wherein the at least
one mount isolator attenuates frequencies greater than 2000 Hz.

[0058] Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the art that
any arrangement, which is calculated to achieve the same purpose, may be
substituted for the specific embodiments shown. Therefore, it is
manifestly intended that this invention be limited only by the claims and
the equivalents thereof.

Patent applications by Todd L. Braman, New Brighton, MN US

Patent applications in class For electronic systems and devices

Patent applications in all subclasses For electronic systems and devices